/*eslint-env es6:false*/
/*
 * Copyright (c) 2010 Arc90 Inc
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*
 * This code is heavily based on Arc90's readability.js (1.7.1) script
 * available at: http://code.google.com/p/arc90labs-readability
 */

/**
 * Public constructor.
 * @param {HTMLDocument} doc     The document to parse.
 * @param {Object}       options The options object.
 */
function Readability(doc, options) {
  // In some older versions, people passed a URI as the first argument. Cope:
  if (options && options.documentElement) {
    doc = options
    options = arguments[2]
  } else if (!doc || !doc.documentElement) {
    throw new Error(
      'First argument to Readability constructor should be a document object.'
    )
  }
  options = options || {}

  this._doc = doc
  this._docJSDOMParser = this._doc.firstChild.__JSDOMParser__
  this._articleTitle = null
  this._articleByline = null
  this._articleDir = null
  this._articleSiteName = null
  this._attempts = []

  // Configurable options
  this._debug = !!options.debug
  this._maxElemsToParse =
    options.maxElemsToParse || this.DEFAULT_MAX_ELEMS_TO_PARSE
  this._nbTopCandidates =
    options.nbTopCandidates || this.DEFAULT_N_TOP_CANDIDATES
  this._charThreshold = options.charThreshold || this.DEFAULT_CHAR_THRESHOLD
  this._classesToPreserve = this.CLASSES_TO_PRESERVE.concat(
    options.classesToPreserve || []
  )
  this._keepClasses = !!options.keepClasses
  this._serializer =
    options.serializer ||
    function(el) {
      return el.innerHTML
    }
  this._disableJSONLD = !!options.disableJSONLD

  // Start with all flags set
  this._flags =
    this.FLAG_STRIP_UNLIKELYS |
    this.FLAG_WEIGHT_CLASSES |
    this.FLAG_CLEAN_CONDITIONALLY

  // Control whether log messages are sent to the console
  if (this._debug) {
    let logNode = function(node) {
      if (node.nodeType == node.TEXT_NODE) {
        return `${node.nodeName} ("${node.textContent}")`
      }
      let attrPairs = Array.from(node.attributes || [], function(attr) {
        return `${attr.name}="${attr.value}"`
      }).join(' ')
      return `<${node.localName} ${attrPairs}>`
    }
    this.log = function() {
      if (typeof dump !== 'undefined') {
        var msg = Array.prototype.map
          .call(arguments, function(x) {
            return x && x.nodeName ? logNode(x) : x
          })
          .join(' ')
        dump('Reader: (Readability) ' + msg + '\n')
      } else if (typeof console !== 'undefined') {
        let args = Array.from(arguments, arg => {
          if (arg && arg.nodeType == this.ELEMENT_NODE) {
            return logNode(arg)
          }
          return arg
        })
        args.unshift('Reader: (Readability)')
        console.log.apply(console, args)
      }
    }
  } else {
    this.log = function() {}
  }
}

Readability.prototype = {
  FLAG_STRIP_UNLIKELYS: 0x1,
  FLAG_WEIGHT_CLASSES: 0x2,
  FLAG_CLEAN_CONDITIONALLY: 0x4,

  // https://developer.mozilla.org/en-US/docs/Web/API/Node/nodeType
  ELEMENT_NODE: 1,
  TEXT_NODE: 3,

  // Max number of nodes supported by this parser. Default: 0 (no limit)
  DEFAULT_MAX_ELEMS_TO_PARSE: 0,

  // The number of top candidates to consider when analysing how
  // tight the competition is among candidates.
  DEFAULT_N_TOP_CANDIDATES: 5,

  // Element tags to score by default.
  DEFAULT_TAGS_TO_SCORE: 'section,h2,h3,h4,h5,h6,p,td,pre'
    .toUpperCase()
    .split(','),

  // The default number of chars an article must have in order to return a result
  DEFAULT_CHAR_THRESHOLD: 500,

  // All of the regular expressions in use within readability.
  // Defined up here so we don't instantiate them repeatedly in loops.
  REGEXPS: {
    // NOTE: These two regular expressions are duplicated in
    // Readability-readerable.js. Please keep both copies in sync.
    unlikelyCandidates: /-ad-|ai2html|banner|breadcrumbs|combx|comment|community|cover-wrap|disqus|extra|footer|gdpr|header|legends|menu|related|remark|replies|rss|shoutbox|sidebar|skyscraper|social|sponsor|supplemental|ad-break|agegate|pagination|pager|popup|yom-remote/i,
    okMaybeItsACandidate: /and|article|body|column|content|main|shadow/i,

    positive: /article|body|content|entry|hentry|h-entry|main|page|pagination|post|text|blog|story/i,
    negative: /-ad-|hidden|^hid$| hid$| hid |^hid |banner|combx|comment|com-|contact|foot|footer|footnote|gdpr|masthead|media|meta|outbrain|promo|related|scroll|share|shoutbox|sidebar|skyscraper|sponsor|shopping|tags|tool|widget/i,
    extraneous: /print|archive|comment|discuss|e[\-]?mail|share|reply|all|login|sign|single|utility/i,
    byline: /byline|author|dateline|writtenby|p-author/i,
    replaceFonts: /<(\/?)font[^>]*>/gi,
    normalize: /\s{2,}/g,
    videos: /\/\/(www\.)?((dailymotion|youtube|youtube-nocookie|player\.vimeo|v\.qq)\.com|(archive|upload\.wikimedia)\.org|player\.twitch\.tv)/i,
    shareElements: /(\b|_)(share|sharedaddy)(\b|_)/i,
    nextLink: /(next|weiter|continue|>([^\|]|$)|»([^\|]|$))/i,
    prevLink: /(prev|earl|old|new|<|«)/i,
    tokenize: /\W+/g,
    whitespace: /^\s*$/,
    hasContent: /\S$/,
    hashUrl: /^#.+/,
    srcsetUrl: /(\S+)(\s+[\d.]+[xw])?(\s*(?:,|$))/g,
    b64DataUrl: /^data:\s*([^\s;,]+)\s*;\s*base64\s*,/i,
    // See: https://schema.org/Article
    jsonLdArticleTypes: /^Article|AdvertiserContentArticle|NewsArticle|AnalysisNewsArticle|AskPublicNewsArticle|BackgroundNewsArticle|OpinionNewsArticle|ReportageNewsArticle|ReviewNewsArticle|Report|SatiricalArticle|ScholarlyArticle|MedicalScholarlyArticle|SocialMediaPosting|BlogPosting|LiveBlogPosting|DiscussionForumPosting|TechArticle|APIReference$/,
  },

  UNLIKELY_ROLES: [
    'menu',
    'menubar',
    'complementary',
    'navigation',
    'alert',
    'alertdialog',
    'dialog',
  ],

  DIV_TO_P_ELEMS: new Set([
    'BLOCKQUOTE',
    'DL',
    'DIV',
    'IMG',
    'OL',
    'P',
    'PRE',
    'TABLE',
    'UL',
  ]),

  ALTER_TO_DIV_EXCEPTIONS: ['DIV', 'ARTICLE', 'SECTION', 'P'],

  PRESENTATIONAL_ATTRIBUTES: [
    'align',
    'background',
    'bgcolor',
    'border',
    'cellpadding',
    'cellspacing',
    'frame',
    'hspace',
    'rules',
    'style',
    'valign',
    'vspace',
  ],

  DEPRECATED_SIZE_ATTRIBUTE_ELEMS: ['TABLE', 'TH', 'TD', 'HR', 'PRE'],

  // The commented out elements qualify as phrasing content but tend to be
  // removed by readability when put into paragraphs, so we ignore them here.
  PHRASING_ELEMS: [
    // "CANVAS", "IFRAME", "SVG", "VIDEO",
    'ABBR',
    'AUDIO',
    'B',
    'BDO',
    'BR',
    'BUTTON',
    'CITE',
    'CODE',
    'DATA',
    'DATALIST',
    'DFN',
    'EM',
    'EMBED',
    'I',
    'IMG',
    'INPUT',
    'KBD',
    'LABEL',
    'MARK',
    'MATH',
    'METER',
    'NOSCRIPT',
    'OBJECT',
    'OUTPUT',
    'PROGRESS',
    'Q',
    'RUBY',
    'SAMP',
    'SCRIPT',
    'SELECT',
    'SMALL',
    'SPAN',
    'STRONG',
    'SUB',
    'SUP',
    'TEXTAREA',
    'TIME',
    'VAR',
    'WBR',
  ],

  // These are the classes that readability sets itself.
  CLASSES_TO_PRESERVE: ['page'],

  // These are the list of HTML entities that need to be escaped.
  HTML_ESCAPE_MAP: {
    lt: '<',
    gt: '>',
    amp: '&',
    quot: '"',
    apos: "'",
  },

  /**
   * Run any post-process modifications to article content as necessary.
   *
   * @param Element
   * @return void
   **/
  _postProcessContent: function(articleContent) {
    // Readability cannot open relative uris so we convert them to absolute uris.
    this._fixRelativeUris(articleContent)

    this._simplifyNestedElements(articleContent)

    if (!this._keepClasses) {
      // Remove classes.
      this._cleanClasses(articleContent)
    }
  },

  /**
   * Iterates over a NodeList, calls `filterFn` for each node and removes node
   * if function returned `true`.
   *
   * If function is not passed, removes all the nodes in node list.
   *
   * @param NodeList nodeList The nodes to operate on
   * @param Function filterFn the function to use as a filter
   * @return void
   */
  _removeNodes: function(nodeList, filterFn) {
    // Avoid ever operating on live node lists.
    if (this._docJSDOMParser && nodeList._isLiveNodeList) {
      throw new Error('Do not pass live node lists to _removeNodes')
    }
    for (var i = nodeList.length - 1; i >= 0; i--) {
      var node = nodeList[i]
      var parentNode = node.parentNode
      if (parentNode) {
        if (!filterFn || filterFn.call(this, node, i, nodeList)) {
          parentNode.removeChild(node)
        }
      }
    }
  },

  /**
   * Iterates over a NodeList, and calls _setNodeTag for each node.
   *
   * @param NodeList nodeList The nodes to operate on
   * @param String newTagName the new tag name to use
   * @return void
   */
  _replaceNodeTags: function(nodeList, newTagName) {
    // Avoid ever operating on live node lists.
    if (this._docJSDOMParser && nodeList._isLiveNodeList) {
      throw new Error('Do not pass live node lists to _replaceNodeTags')
    }
    for (const node of nodeList) {
      this._setNodeTag(node, newTagName)
    }
  },

  /**
   * Iterate over a NodeList, which doesn't natively fully implement the Array
   * interface.
   *
   * For convenience, the current object context is applied to the provided
   * iterate function.
   *
   * @param  NodeList nodeList The NodeList.
   * @param  Function fn       The iterate function.
   * @return void
   */
  _forEachNode: function(nodeList, fn) {
    Array.prototype.forEach.call(nodeList, fn, this)
  },

  /**
   * Iterate over a NodeList, and return the first node that passes
   * the supplied test function
   *
   * For convenience, the current object context is applied to the provided
   * test function.
   *
   * @param  NodeList nodeList The NodeList.
   * @param  Function fn       The test function.
   * @return void
   */
  _findNode: function(nodeList, fn) {
    return Array.prototype.find.call(nodeList, fn, this)
  },

  /**
   * Iterate over a NodeList, return true if any of the provided iterate
   * function calls returns true, false otherwise.
   *
   * For convenience, the current object context is applied to the
   * provided iterate function.
   *
   * @param  NodeList nodeList The NodeList.
   * @param  Function fn       The iterate function.
   * @return Boolean
   */
  _someNode: function(nodeList, fn) {
    return Array.prototype.some.call(nodeList, fn, this)
  },

  /**
   * Iterate over a NodeList, return true if all of the provided iterate
   * function calls return true, false otherwise.
   *
   * For convenience, the current object context is applied to the
   * provided iterate function.
   *
   * @param  NodeList nodeList The NodeList.
   * @param  Function fn       The iterate function.
   * @return Boolean
   */
  _everyNode: function(nodeList, fn) {
    return Array.prototype.every.call(nodeList, fn, this)
  },

  /**
   * Concat all nodelists passed as arguments.
   *
   * @return ...NodeList
   * @return Array
   */
  _concatNodeLists: function() {
    var slice = Array.prototype.slice
    var args = slice.call(arguments)
    var nodeLists = args.map(function(list) {
      return slice.call(list)
    })
    return Array.prototype.concat.apply([], nodeLists)
  },

  _getAllNodesWithTag: function(node, tagNames) {
    if (node.querySelectorAll) {
      return node.querySelectorAll(tagNames.join(','))
    }
    return [].concat.apply(
      [],
      tagNames.map(function(tag) {
        var collection = node.getElementsByTagName(tag)
        return Array.isArray(collection) ? collection : Array.from(collection)
      })
    )
  },

  /**
   * Removes the class="" attribute from every element in the given
   * subtree, except those that match CLASSES_TO_PRESERVE and
   * the classesToPreserve array from the options object.
   *
   * @param Element
   * @return void
   */
  _cleanClasses: function(node) {
    var classesToPreserve = this._classesToPreserve
    var className = (node.getAttribute('class') || '')
      .split(/\s+/)
      .filter(function(cls) {
        return classesToPreserve.indexOf(cls) != -1
      })
      .join(' ')

    if (className) {
      node.setAttribute('class', className)
    } else {
      node.removeAttribute('class')
    }

    for (node = node.firstElementChild; node; node = node.nextElementSibling) {
      this._cleanClasses(node)
    }
  },

  /**
   * Converts each <a> and <img> uri in the given element to an absolute URI,
   * ignoring #ref URIs.
   *
   * @param Element
   * @return void
   */
  _fixRelativeUris: function(articleContent) {
    var baseURI = this._doc.baseURI
    var documentURI = this._doc.documentURI
    function toAbsoluteURI(uri) {
      // Leave hash links alone if the base URI matches the document URI:
      if (baseURI == documentURI && uri.charAt(0) == '#') {
        return uri
      }

      // Otherwise, resolve against base URI:
      try {
        return new URL(uri, baseURI).href
      } catch (ex) {
        // Something went wrong, just return the original:
      }
      return uri
    }

    var links = this._getAllNodesWithTag(articleContent, ['a'])
    this._forEachNode(links, function(link) {
      var href = link.getAttribute('href')
      if (href) {
        // Remove links with javascript: URIs, since
        // they won't work after scripts have been removed from the page.
        if (href.indexOf('javascript:') === 0) {
          // if the link only contains simple text content, it can be converted to a text node
          if (
            link.childNodes.length === 1 &&
            link.childNodes[0].nodeType === this.TEXT_NODE
          ) {
            var text = this._doc.createTextNode(link.textContent)
            link.parentNode.replaceChild(text, link)
          } else {
            // if the link has multiple children, they should all be preserved
            var container = this._doc.createElement('span')
            while (link.childNodes.length > 0) {
              container.appendChild(link.childNodes[0])
            }
            link.parentNode.replaceChild(container, link)
          }
        } else {
          link.setAttribute('href', toAbsoluteURI(href))
        }
      }
    })

    var medias = this._getAllNodesWithTag(articleContent, [
      'img',
      'picture',
      'figure',
      'video',
      'audio',
      'source',
    ])

    this._forEachNode(medias, function(media) {
      var src = media.getAttribute('src')
      var poster = media.getAttribute('poster')
      var srcset = media.getAttribute('srcset')

      if (src) {
        media.setAttribute('src', toAbsoluteURI(src))
      }

      if (poster) {
        media.setAttribute('poster', toAbsoluteURI(poster))
      }

      if (srcset) {
        var newSrcset = srcset.replace(this.REGEXPS.srcsetUrl, function(
          _,
          p1,
          p2,
          p3
        ) {
          return toAbsoluteURI(p1) + (p2 || '') + p3
        })

        media.setAttribute('srcset', newSrcset)
      }
    })
  },

  _simplifyNestedElements: function(articleContent) {
    var node = articleContent

    while (node) {
      if (
        node.parentNode &&
        ['DIV', 'SECTION'].includes(node.tagName) &&
        !(node.id && node.id.startsWith('readability'))
      ) {
        if (this._isElementWithoutContent(node)) {
          node = this._removeAndGetNext(node)
          continue
        } else if (
          this._hasSingleTagInsideElement(node, 'DIV') ||
          this._hasSingleTagInsideElement(node, 'SECTION')
        ) {
          var child = node.children[0]
          for (var i = 0; i < node.attributes.length; i++) {
            child.setAttribute(
              node.attributes[i].name,
              node.attributes[i].value
            )
          }
          node.parentNode.replaceChild(child, node)
          node = child
          continue
        }
      }

      node = this._getNextNode(node)
    }
  },

  /**
   * Get the article title as an H1.
   *
   * @return string
   **/
  _getArticleTitle: function() {
    var doc = this._doc
    var curTitle = ''
    var origTitle = ''

    try {
      curTitle = origTitle = doc.title.trim()

      // If they had an element with id "title" in their HTML
      if (typeof curTitle !== 'string')
        curTitle = origTitle = this._getInnerText(
          doc.getElementsByTagName('title')[0]
        )
    } catch (e) {
      /* ignore exceptions setting the title. */
    }

    var titleHadHierarchicalSeparators = false
    function wordCount(str) {
      return str.split(/\s+/).length
    }

    // If there's a separator in the title, first remove the final part
    if (/ [\|\-\\\/>»] /.test(curTitle)) {
      titleHadHierarchicalSeparators = / [\\\/>»] /.test(curTitle)
      curTitle = origTitle.replace(/(.*)[\|\-\\\/>»] .*/gi, '$1')

      // If the resulting title is too short (3 words or fewer), remove
      // the first part instead:
      if (wordCount(curTitle) < 3)
        curTitle = origTitle.replace(/[^\|\-\\\/>»]*[\|\-\\\/>»](.*)/gi, '$1')
    } else if (curTitle.indexOf(': ') !== -1) {
      // Check if we have an heading containing this exact string, so we
      // could assume it's the full title.
      var headings = this._concatNodeLists(
        doc.getElementsByTagName('h1'),
        doc.getElementsByTagName('h2')
      )
      var trimmedTitle = curTitle.trim()
      var match = this._someNode(headings, function(heading) {
        return heading.textContent.trim() === trimmedTitle
      })

      // If we don't, let's extract the title out of the original title string.
      if (!match) {
        curTitle = origTitle.substring(origTitle.lastIndexOf(':') + 1)

        // If the title is now too short, try the first colon instead:
        if (wordCount(curTitle) < 3) {
          curTitle = origTitle.substring(origTitle.indexOf(':') + 1)
          // But if we have too many words before the colon there's something weird
          // with the titles and the H tags so let's just use the original title instead
        } else if (wordCount(origTitle.substr(0, origTitle.indexOf(':'))) > 5) {
          curTitle = origTitle
        }
      }
    } else if (curTitle.length > 150 || curTitle.length < 15) {
      var hOnes = doc.getElementsByTagName('h1')

      if (hOnes.length === 1) curTitle = this._getInnerText(hOnes[0])
    }

    curTitle = curTitle.trim().replace(this.REGEXPS.normalize, ' ')
    // If we now have 4 words or fewer as our title, and either no
    // 'hierarchical' separators (\, /, > or ») were found in the original
    // title or we decreased the number of words by more than 1 word, use
    // the original title.
    var curTitleWordCount = wordCount(curTitle)
    if (
      curTitleWordCount <= 4 &&
      (!titleHadHierarchicalSeparators ||
        curTitleWordCount !=
          wordCount(origTitle.replace(/[\|\-\\\/>»]+/g, '')) - 1)
    ) {
      curTitle = origTitle
    }

    return curTitle
  },

  /**
   * Prepare the HTML document for readability to scrape it.
   * This includes things like stripping javascript, CSS, and handling terrible markup.
   *
   * @return void
   **/
  _prepDocument: function() {
    var doc = this._doc

    // Remove all style tags in head
    this._removeNodes(this._getAllNodesWithTag(doc, ['style']))

    if (doc.body) {
      this._replaceBrs(doc.body)
    }

    this._replaceNodeTags(this._getAllNodesWithTag(doc, ['font']), 'SPAN')
  },

  /**
   * Finds the next node, starting from the given node, and ignoring
   * whitespace in between. If the given node is an element, the same node is
   * returned.
   */
  _nextNode: function(node) {
    var next = node
    while (
      next &&
      next.nodeType != this.ELEMENT_NODE &&
      this.REGEXPS.whitespace.test(next.textContent)
    ) {
      next = next.nextSibling
    }
    return next
  },

  /**
   * Replaces 2 or more successive <br> elements with a single <p>.
   * Whitespace between <br> elements are ignored. For example:
   *   <div>foo<br>bar<br> <br><br>abc</div>
   * will become:
   *   <div>foo<br>bar<p>abc</p></div>
   */
  _replaceBrs: function(elem) {
    this._forEachNode(this._getAllNodesWithTag(elem, ['br']), function(br) {
      var next = br.nextSibling

      // Whether 2 or more <br> elements have been found and replaced with a
      // <p> block.
      var replaced = false

      // If we find a <br> chain, remove the <br>s until we hit another node
      // or non-whitespace. This leaves behind the first <br> in the chain
      // (which will be replaced with a <p> later).
      while ((next = this._nextNode(next)) && next.tagName == 'BR') {
        replaced = true
        var brSibling = next.nextSibling
        next.parentNode.removeChild(next)
        next = brSibling
      }

      // If we removed a <br> chain, replace the remaining <br> with a <p>. Add
      // all sibling nodes as children of the <p> until we hit another <br>
      // chain.
      if (replaced) {
        var p = this._doc.createElement('p')
        br.parentNode.replaceChild(p, br)

        next = p.nextSibling
        while (next) {
          // If we've hit another <br><br>, we're done adding children to this <p>.
          if (next.tagName == 'BR') {
            var nextElem = this._nextNode(next.nextSibling)
            if (nextElem && nextElem.tagName == 'BR') break
          }

          if (!this._isPhrasingContent(next)) break

          // Otherwise, make this node a child of the new <p>.
          var sibling = next.nextSibling
          p.appendChild(next)
          next = sibling
        }

        while (p.lastChild && this._isWhitespace(p.lastChild)) {
          p.removeChild(p.lastChild)
        }

        if (p.parentNode.tagName === 'P') this._setNodeTag(p.parentNode, 'DIV')
      }
    })
  },

  _setNodeTag: function(node, tag) {
    this.log('_setNodeTag', node, tag)
    if (this._docJSDOMParser) {
      node.localName = tag.toLowerCase()
      node.tagName = tag.toUpperCase()
      return node
    }

    var replacement = node.ownerDocument.createElement(tag)
    while (node.firstChild) {
      replacement.appendChild(node.firstChild)
    }
    node.parentNode.replaceChild(replacement, node)
    if (node.readability) replacement.readability = node.readability

    for (var i = 0; i < node.attributes.length; i++) {
      try {
        replacement.setAttribute(
          node.attributes[i].name,
          node.attributes[i].value
        )
      } catch (ex) {
        /* it's possible for setAttribute() to throw if the attribute name
         * isn't a valid XML Name. Such attributes can however be parsed from
         * source in HTML docs, see https://github.com/whatwg/html/issues/4275,
         * so we can hit them here and then throw. We don't care about such
         * attributes so we ignore them.
         */
      }
    }
    return replacement
  },

  /**
   * Prepare the article node for display. Clean out any inline styles,
   * iframes, forms, strip extraneous <p> tags, etc.
   *
   * @param Element
   * @return void
   **/
  _prepArticle: function(articleContent) {
    this._cleanStyles(articleContent)

    // Check for data tables before we continue, to avoid removing items in
    // those tables, which will often be isolated even though they're
    // visually linked to other content-ful elements (text, images, etc.).
    this._markDataTables(articleContent)

    this._fixLazyImages(articleContent)

    // Clean out junk from the article content
    this._cleanConditionally(articleContent, 'form')
    this._cleanConditionally(articleContent, 'fieldset')
    this._clean(articleContent, 'object')
    this._clean(articleContent, 'embed')
    this._clean(articleContent, 'footer')
    this._clean(articleContent, 'link')
    this._clean(articleContent, 'aside')

    // Clean out elements with little content that have "share" in their id/class combinations from final top candidates,
    // which means we don't remove the top candidates even they have "share".

    var shareElementThreshold = this.DEFAULT_CHAR_THRESHOLD

    this._forEachNode(articleContent.children, function(topCandidate) {
      this._cleanMatchedNodes(topCandidate, function(node, matchString) {
        return (
          this.REGEXPS.shareElements.test(matchString) &&
          node.textContent.length < shareElementThreshold
        )
      })
    })

    this._clean(articleContent, 'iframe')
    this._clean(articleContent, 'input')
    this._clean(articleContent, 'textarea')
    this._clean(articleContent, 'select')
    this._clean(articleContent, 'button')
    this._cleanHeaders(articleContent)

    // Do these last as the previous stuff may have removed junk
    // that will affect these
    this._cleanConditionally(articleContent, 'table')
    this._cleanConditionally(articleContent, 'ul')
    this._cleanConditionally(articleContent, 'div')

    // replace H1 with H2 as H1 should be only title that is displayed separately
    this._replaceNodeTags(
      this._getAllNodesWithTag(articleContent, ['h1']),
      'h2'
    )

    // Remove extra paragraphs
    this._removeNodes(this._getAllNodesWithTag(articleContent, ['p']), function(
      paragraph
    ) {
      var imgCount = paragraph.getElementsByTagName('img').length
      var embedCount = paragraph.getElementsByTagName('embed').length
      var objectCount = paragraph.getElementsByTagName('object').length
      // At this point, nasty iframes have been removed, only remain embedded video ones.
      var iframeCount = paragraph.getElementsByTagName('iframe').length
      var totalCount = imgCount + embedCount + objectCount + iframeCount

      return totalCount === 0 && !this._getInnerText(paragraph, false)
    })

    this._forEachNode(
      this._getAllNodesWithTag(articleContent, ['br']),
      function(br) {
        var next = this._nextNode(br.nextSibling)
        if (next && next.tagName == 'P') br.parentNode.removeChild(br)
      }
    )

    // Remove single-cell tables
    this._forEachNode(
      this._getAllNodesWithTag(articleContent, ['table']),
      function(table) {
        var tbody = this._hasSingleTagInsideElement(table, 'TBODY')
          ? table.firstElementChild
          : table
        if (this._hasSingleTagInsideElement(tbody, 'TR')) {
          var row = tbody.firstElementChild
          if (this._hasSingleTagInsideElement(row, 'TD')) {
            var cell = row.firstElementChild
            cell = this._setNodeTag(
              cell,
              this._everyNode(cell.childNodes, this._isPhrasingContent)
                ? 'P'
                : 'DIV'
            )
            table.parentNode.replaceChild(cell, table)
          }
        }
      }
    )
  },

  /**
   * Initialize a node with the readability object. Also checks the
   * className/id for special names to add to its score.
   *
   * @param Element
   * @return void
   **/
  _initializeNode: function(node) {
    node.readability = { contentScore: 0 }

    switch (node.tagName) {
      case 'DIV':
        node.readability.contentScore += 5
        break

      case 'PRE':
      case 'TD':
      case 'BLOCKQUOTE':
        node.readability.contentScore += 3
        break

      case 'ADDRESS':
      case 'OL':
      case 'UL':
      case 'DL':
      case 'DD':
      case 'DT':
      case 'LI':
      case 'FORM':
        node.readability.contentScore -= 3
        break

      case 'H1':
      case 'H2':
      case 'H3':
      case 'H4':
      case 'H5':
      case 'H6':
      case 'TH':
        node.readability.contentScore -= 5
        break
    }

    node.readability.contentScore += this._getClassWeight(node)
  },

  _removeAndGetNext: function(node) {
    var nextNode = this._getNextNode(node, true)
    node.parentNode.removeChild(node)
    return nextNode
  },

  /**
   * Traverse the DOM from node to node, starting at the node passed in.
   * Pass true for the second parameter to indicate this node itself
   * (and its kids) are going away, and we want the next node over.
   *
   * Calling this in a loop will traverse the DOM depth-first.
   */
  _getNextNode: function(node, ignoreSelfAndKids) {
    // First check for kids if those aren't being ignored
    if (!ignoreSelfAndKids && node.firstElementChild) {
      return node.firstElementChild
    }
    // Then for siblings...
    if (node.nextElementSibling) {
      return node.nextElementSibling
    }
    // And finally, move up the parent chain *and* find a sibling
    // (because this is depth-first traversal, we will have already
    // seen the parent nodes themselves).
    do {
      node = node.parentNode
    } while (node && !node.nextElementSibling)
    return node && node.nextElementSibling
  },

  // compares second text to first one
  // 1 = same text, 0 = completely different text
  // works the way that it splits both texts into words and then finds words that are unique in second text
  // the result is given by the lower length of unique parts
  _textSimilarity: function(textA, textB) {
    var tokensA = textA
      .toLowerCase()
      .split(this.REGEXPS.tokenize)
      .filter(Boolean)
    var tokensB = textB
      .toLowerCase()
      .split(this.REGEXPS.tokenize)
      .filter(Boolean)
    if (!tokensA.length || !tokensB.length) {
      return 0
    }
    var uniqTokensB = tokensB.filter(token => !tokensA.includes(token))
    var distanceB = uniqTokensB.join(' ').length / tokensB.join(' ').length
    return 1 - distanceB
  },

  _checkByline: function(node, matchString) {
    if (this._articleByline) {
      return false
    }

    if (node.getAttribute !== undefined) {
      var rel = node.getAttribute('rel')
      var itemprop = node.getAttribute('itemprop')
    }

    if (
      (rel === 'author' ||
        (itemprop && itemprop.indexOf('author') !== -1) ||
        this.REGEXPS.byline.test(matchString)) &&
      this._isValidByline(node.textContent)
    ) {
      this._articleByline = node.textContent.trim()
      return true
    }

    return false
  },

  _getNodeAncestors: function(node, maxDepth) {
    maxDepth = maxDepth || 0
    var i = 0,
      ancestors = []
    while (node.parentNode) {
      ancestors.push(node.parentNode)
      if (maxDepth && ++i === maxDepth) break
      node = node.parentNode
    }
    return ancestors
  },

  /***
   * grabArticle - Using a variety of metrics (content score, classname, element types), find the content that is
   *         most likely to be the stuff a user wants to read. Then return it wrapped up in a div.
   *
   * @param page a document to run upon. Needs to be a full document, complete with body.
   * @return Element
   **/
  _grabArticle: function(page) {
    this.log('**** grabArticle ****')
    var doc = this._doc
    var isPaging = page !== null
    page = page ? page : this._doc.body

    // We can't grab an article if we don't have a page!
    if (!page) {
      this.log('No body found in document. Abort.')
      return null
    }

    var pageCacheHtml = page.innerHTML

    while (true) {
      this.log('Starting grabArticle loop')
      var stripUnlikelyCandidates = this._flagIsActive(
        this.FLAG_STRIP_UNLIKELYS
      )

      // First, node prepping. Trash nodes that look cruddy (like ones with the
      // class name "comment", etc), and turn divs into P tags where they have been
      // used inappropriately (as in, where they contain no other block level elements.)
      var elementsToScore = []
      var node = this._doc.documentElement

      let shouldRemoveTitleHeader = true

      while (node) {
        var matchString = node.className + ' ' + node.id

        if (!this._isProbablyVisible(node)) {
          this.log('Removing hidden node - ' + matchString)
          node = this._removeAndGetNext(node)
          continue
        }

        // Check to see if this node is a byline, and remove it if it is.
        if (this._checkByline(node, matchString)) {
          node = this._removeAndGetNext(node)
          continue
        }

        if (shouldRemoveTitleHeader && this._headerDuplicatesTitle(node)) {
          this.log(
            'Removing header: ',
            node.textContent.trim(),
            this._articleTitle.trim()
          )
          shouldRemoveTitleHeader = false
          node = this._removeAndGetNext(node)
          continue
        }

        // Remove unlikely candidates
        if (stripUnlikelyCandidates) {
          if (
            this.REGEXPS.unlikelyCandidates.test(matchString) &&
            !this.REGEXPS.okMaybeItsACandidate.test(matchString) &&
            !this._hasAncestorTag(node, 'table') &&
            !this._hasAncestorTag(node, 'code') &&
            node.tagName !== 'BODY' &&
            node.tagName !== 'A'
          ) {
            this.log('Removing unlikely candidate - ' + matchString)
            node = this._removeAndGetNext(node)
            continue
          }

          if (this.UNLIKELY_ROLES.includes(node.getAttribute('role'))) {
            this.log(
              'Removing content with role ' +
                node.getAttribute('role') +
                ' - ' +
                matchString
            )
            node = this._removeAndGetNext(node)
            continue
          }
        }

        // Remove DIV, SECTION, and HEADER nodes without any content(e.g. text, image, video, or iframe).
        if (
          (node.tagName === 'DIV' ||
            node.tagName === 'SECTION' ||
            node.tagName === 'HEADER' ||
            node.tagName === 'H1' ||
            node.tagName === 'H2' ||
            node.tagName === 'H3' ||
            node.tagName === 'H4' ||
            node.tagName === 'H5' ||
            node.tagName === 'H6') &&
          this._isElementWithoutContent(node)
        ) {
          node = this._removeAndGetNext(node)
          continue
        }

        if (this.DEFAULT_TAGS_TO_SCORE.indexOf(node.tagName) !== -1) {
          elementsToScore.push(node)
        }

        // Turn all divs that don't have children block level elements into p's
        if (node.tagName === 'DIV') {
          // Put phrasing content into paragraphs.
          var p = null
          var childNode = node.firstChild
          while (childNode) {
            var nextSibling = childNode.nextSibling
            if (this._isPhrasingContent(childNode)) {
              if (p !== null) {
                p.appendChild(childNode)
              } else if (!this._isWhitespace(childNode)) {
                p = doc.createElement('p')
                node.replaceChild(p, childNode)
                p.appendChild(childNode)
              }
            } else if (p !== null) {
              while (p.lastChild && this._isWhitespace(p.lastChild)) {
                p.removeChild(p.lastChild)
              }
              p = null
            }
            childNode = nextSibling
          }

          // Sites like http://mobile.slate.com encloses each paragraph with a DIV
          // element. DIVs with only a P element inside and no text content can be
          // safely converted into plain P elements to avoid confusing the scoring
          // algorithm with DIVs with are, in practice, paragraphs.
          if (
            this._hasSingleTagInsideElement(node, 'P') &&
            this._getLinkDensity(node) < 0.25
          ) {
            var newNode = node.children[0]
            node.parentNode.replaceChild(newNode, node)
            node = newNode
            elementsToScore.push(node)
          } else if (!this._hasChildBlockElement(node)) {
            node = this._setNodeTag(node, 'P')
            elementsToScore.push(node)
          }
        }
        node = this._getNextNode(node)
      }

      /**
       * Loop through all paragraphs, and assign a score to them based on how content-y they look.
       * Then add their score to their parent node.
       *
       * A score is determined by things like number of commas, class names, etc. Maybe eventually link density.
       **/
      var candidates = []
      this._forEachNode(elementsToScore, function(elementToScore) {
        if (
          !elementToScore.parentNode ||
          typeof elementToScore.parentNode.tagName === 'undefined'
        )
          return

        // If this paragraph is less than 25 characters, don't even count it.
        var innerText = this._getInnerText(elementToScore)
        if (innerText.length < 25) return

        // Exclude nodes with no ancestor.
        var ancestors = this._getNodeAncestors(elementToScore, 5)
        if (ancestors.length === 0) return

        var contentScore = 0

        // Add a point for the paragraph itself as a base.
        contentScore += 1

        // Add points for any commas within this paragraph.
        contentScore += innerText.split(',').length

        // For every 100 characters in this paragraph, add another point. Up to 3 points.
        contentScore += Math.min(Math.floor(innerText.length / 100), 3)

        // Initialize and score ancestors.
        this._forEachNode(ancestors, function(ancestor, level) {
          if (
            !ancestor.tagName ||
            !ancestor.parentNode ||
            typeof ancestor.parentNode.tagName === 'undefined'
          )
            return

          if (typeof ancestor.readability === 'undefined') {
            this._initializeNode(ancestor)
            candidates.push(ancestor)
          }

          // Node score divider:
          // - parent:             1 (no division)
          // - grandparent:        2
          // - great grandparent+: ancestor level * 3
          if (level === 0) var scoreDivider = 1
          else if (level === 1) scoreDivider = 2
          else scoreDivider = level * 3
          ancestor.readability.contentScore += contentScore / scoreDivider
        })
      })

      // After we've calculated scores, loop through all of the possible
      // candidate nodes we found and find the one with the highest score.
      var topCandidates = []
      for (var c = 0, cl = candidates.length; c < cl; c += 1) {
        var candidate = candidates[c]

        // Scale the final candidates score based on link density. Good content
        // should have a relatively small link density (5% or less) and be mostly
        // unaffected by this operation.
        var candidateScore =
          candidate.readability.contentScore *
          (1 - this._getLinkDensity(candidate))
        candidate.readability.contentScore = candidateScore

        this.log('Candidate:', candidate, 'with score ' + candidateScore)

        for (var t = 0; t < this._nbTopCandidates; t++) {
          var aTopCandidate = topCandidates[t]

          if (
            !aTopCandidate ||
            candidateScore > aTopCandidate.readability.contentScore
          ) {
            topCandidates.splice(t, 0, candidate)
            if (topCandidates.length > this._nbTopCandidates)
              topCandidates.pop()
            break
          }
        }
      }

      var topCandidate = topCandidates[0] || null
      var neededToCreateTopCandidate = false
      var parentOfTopCandidate

      // If we still have no top candidate, just use the body as a last resort.
      // We also have to copy the body node so it is something we can modify.
      if (topCandidate === null || topCandidate.tagName === 'BODY') {
        // Move all of the page's children into topCandidate
        topCandidate = doc.createElement('DIV')
        neededToCreateTopCandidate = true
        // Move everything (not just elements, also text nodes etc.) into the container
        // so we even include text directly in the body:
        var kids = page.childNodes
        while (kids.length) {
          this.log('Moving child out:', kids[0])
          topCandidate.appendChild(kids[0])
        }

        page.appendChild(topCandidate)

        this._initializeNode(topCandidate)
      } else if (topCandidate) {
        // Find a better top candidate node if it contains (at least three) nodes which belong to `topCandidates` array
        // and whose scores are quite closed with current `topCandidate` node.
        var alternativeCandidateAncestors = []
        for (var i = 1; i < topCandidates.length; i++) {
          if (
            topCandidates[i].readability.contentScore /
              topCandidate.readability.contentScore >=
            0.75
          ) {
            alternativeCandidateAncestors.push(
              this._getNodeAncestors(topCandidates[i])
            )
          }
        }
        var MINIMUM_TOPCANDIDATES = 3
        if (alternativeCandidateAncestors.length >= MINIMUM_TOPCANDIDATES) {
          parentOfTopCandidate = topCandidate.parentNode
          while (parentOfTopCandidate.tagName !== 'BODY') {
            var listsContainingThisAncestor = 0
            for (
              var ancestorIndex = 0;
              ancestorIndex < alternativeCandidateAncestors.length &&
              listsContainingThisAncestor < MINIMUM_TOPCANDIDATES;
              ancestorIndex++
            ) {
              listsContainingThisAncestor += Number(
                alternativeCandidateAncestors[ancestorIndex].includes(
                  parentOfTopCandidate
                )
              )
            }
            if (listsContainingThisAncestor >= MINIMUM_TOPCANDIDATES) {
              topCandidate = parentOfTopCandidate
              break
            }
            parentOfTopCandidate = parentOfTopCandidate.parentNode
          }
        }
        if (!topCandidate.readability) {
          this._initializeNode(topCandidate)
        }

        // Because of our bonus system, parents of candidates might have scores
        // themselves. They get half of the node. There won't be nodes with higher
        // scores than our topCandidate, but if we see the score going *up* in the first
        // few steps up the tree, that's a decent sign that there might be more content
        // lurking in other places that we want to unify in. The sibling stuff
        // below does some of that - but only if we've looked high enough up the DOM
        // tree.
        parentOfTopCandidate = topCandidate.parentNode
        var lastScore = topCandidate.readability.contentScore
        // The scores shouldn't get too low.
        var scoreThreshold = lastScore / 3
        while (parentOfTopCandidate.tagName !== 'BODY') {
          if (!parentOfTopCandidate.readability) {
            parentOfTopCandidate = parentOfTopCandidate.parentNode
            continue
          }
          var parentScore = parentOfTopCandidate.readability.contentScore
          if (parentScore < scoreThreshold) break
          if (parentScore > lastScore) {
            // Alright! We found a better parent to use.
            topCandidate = parentOfTopCandidate
            break
          }
          lastScore = parentOfTopCandidate.readability.contentScore
          parentOfTopCandidate = parentOfTopCandidate.parentNode
        }

        // If the top candidate is the only child, use parent instead. This will help sibling
        // joining logic when adjacent content is actually located in parent's sibling node.
        parentOfTopCandidate = topCandidate.parentNode
        while (
          parentOfTopCandidate.tagName != 'BODY' &&
          parentOfTopCandidate.children.length == 1
        ) {
          topCandidate = parentOfTopCandidate
          parentOfTopCandidate = topCandidate.parentNode
        }
        if (!topCandidate.readability) {
          this._initializeNode(topCandidate)
        }
      }

      // Now that we have the top candidate, look through its siblings for content
      // that might also be related. Things like preambles, content split by ads
      // that we removed, etc.
      var articleContent = doc.createElement('DIV')
      if (isPaging) articleContent.id = 'readability-content'

      var siblingScoreThreshold = Math.max(
        10,
        topCandidate.readability.contentScore * 0.2
      )
      // Keep potential top candidate's parent node to try to get text direction of it later.
      parentOfTopCandidate = topCandidate.parentNode
      var siblings = parentOfTopCandidate.children

      for (var s = 0, sl = siblings.length; s < sl; s++) {
        var sibling = siblings[s]
        var append = false

        this.log(
          'Looking at sibling node:',
          sibling,
          sibling.readability
            ? 'with score ' + sibling.readability.contentScore
            : ''
        )
        this.log(
          'Sibling has score',
          sibling.readability ? sibling.readability.contentScore : 'Unknown'
        )

        if (sibling === topCandidate) {
          append = true
        } else {
          var contentBonus = 0

          // Give a bonus if sibling nodes and top candidates have the example same classname
          if (
            sibling.className === topCandidate.className &&
            topCandidate.className !== ''
          )
            contentBonus += topCandidate.readability.contentScore * 0.2

          if (
            sibling.readability &&
            sibling.readability.contentScore + contentBonus >=
              siblingScoreThreshold
          ) {
            append = true
          } else if (sibling.nodeName === 'P') {
            var linkDensity = this._getLinkDensity(sibling)
            var nodeContent = this._getInnerText(sibling)
            var nodeLength = nodeContent.length

            if (nodeLength > 80 && linkDensity < 0.25) {
              append = true
            } else if (
              nodeLength < 80 &&
              nodeLength > 0 &&
              linkDensity === 0 &&
              nodeContent.search(/\.( |$)/) !== -1
            ) {
              append = true
            }
          }
        }

        if (append) {
          this.log('Appending node:', sibling)

          if (this.ALTER_TO_DIV_EXCEPTIONS.indexOf(sibling.nodeName) === -1) {
            // We have a node that isn't a common block level element, like a form or td tag.
            // Turn it into a div so it doesn't get filtered out later by accident.
            this.log('Altering sibling:', sibling, 'to div.')

            sibling = this._setNodeTag(sibling, 'DIV')
          }

          articleContent.appendChild(sibling)
          // siblings is a reference to the children array, and
          // sibling is removed from the array when we call appendChild().
          // As a result, we must revisit this index since the nodes
          // have been shifted.
          s -= 1
          sl -= 1
        }
      }

      if (this._debug)
        this.log('Article content pre-prep: ' + articleContent.innerHTML)
      // So we have all of the content that we need. Now we clean it up for presentation.
      this._prepArticle(articleContent)
      if (this._debug)
        this.log('Article content post-prep: ' + articleContent.innerHTML)

      if (neededToCreateTopCandidate) {
        // We already created a fake div thing, and there wouldn't have been any siblings left
        // for the previous loop, so there's no point trying to create a new div, and then
        // move all the children over. Just assign IDs and class names here. No need to append
        // because that already happened anyway.
        topCandidate.id = 'readability-page-1'
        topCandidate.className = 'page'
      } else {
        var div = doc.createElement('DIV')
        div.id = 'readability-page-1'
        div.className = 'page'
        var children = articleContent.childNodes
        while (children.length) {
          div.appendChild(children[0])
        }
        articleContent.appendChild(div)
      }

      if (this._debug)
        this.log('Article content after paging: ' + articleContent.innerHTML)

      var parseSuccessful = true

      // Now that we've gone through the full algorithm, check to see if
      // we got any meaningful content. If we didn't, we may need to re-run
      // grabArticle with different flags set. This gives us a higher likelihood of
      // finding the content, and the sieve approach gives us a higher likelihood of
      // finding the -right- content.
      var textLength = this._getInnerText(articleContent, true).length
      if (textLength < this._charThreshold) {
        parseSuccessful = false
        page.innerHTML = pageCacheHtml

        if (this._flagIsActive(this.FLAG_STRIP_UNLIKELYS)) {
          this._removeFlag(this.FLAG_STRIP_UNLIKELYS)
          this._attempts.push({
            articleContent: articleContent,
            textLength: textLength,
          })
        } else if (this._flagIsActive(this.FLAG_WEIGHT_CLASSES)) {
          this._removeFlag(this.FLAG_WEIGHT_CLASSES)
          this._attempts.push({
            articleContent: articleContent,
            textLength: textLength,
          })
        } else if (this._flagIsActive(this.FLAG_CLEAN_CONDITIONALLY)) {
          this._removeFlag(this.FLAG_CLEAN_CONDITIONALLY)
          this._attempts.push({
            articleContent: articleContent,
            textLength: textLength,
          })
        } else {
          this._attempts.push({
            articleContent: articleContent,
            textLength: textLength,
          })
          // No luck after removing flags, just return the longest text we found during the different loops
          this._attempts.sort(function(a, b) {
            return b.textLength - a.textLength
          })

          // But first check if we actually have something
          if (!this._attempts[0].textLength) {
            return null
          }

          articleContent = this._attempts[0].articleContent
          parseSuccessful = true
        }
      }

      if (parseSuccessful) {
        // Find out text direction from ancestors of final top candidate.
        var ancestors = [parentOfTopCandidate, topCandidate].concat(
          this._getNodeAncestors(parentOfTopCandidate)
        )
        this._someNode(ancestors, function(ancestor) {
          if (!ancestor.tagName) return false
          var articleDir = ancestor.getAttribute('dir')
          if (articleDir) {
            this._articleDir = articleDir
            return true
          }
          return false
        })
        return articleContent
      }
    }
  },

  /**
   * Check whether the input string could be a byline.
   * This verifies that the input is a string, and that the length
   * is less than 100 chars.
   *
   * @param possibleByline {string} - a string to check whether its a byline.
   * @return Boolean - whether the input string is a byline.
   */
  _isValidByline: function(byline) {
    if (typeof byline == 'string' || byline instanceof String) {
      byline = byline.trim()
      return byline.length > 0 && byline.length < 100
    }
    return false
  },

  /**
   * Converts some of the common HTML entities in string to their corresponding characters.
   *
   * @param str {string} - a string to unescape.
   * @return string without HTML entity.
   */
  _unescapeHtmlEntities: function(str) {
    if (!str) {
      return str
    }

    var htmlEscapeMap = this.HTML_ESCAPE_MAP
    return str
      .replace(/&(quot|amp|apos|lt|gt);/g, function(_, tag) {
        return htmlEscapeMap[tag]
      })
      .replace(/&#(?:x([0-9a-z]{1,4})|([0-9]{1,4}));/gi, function(
        _,
        hex,
        numStr
      ) {
        var num = parseInt(hex || numStr, hex ? 16 : 10)
        return String.fromCharCode(num)
      })
  },

  /**
   * Try to extract metadata from JSON-LD object.
   * For now, only Schema.org objects of type Article or its subtypes are supported.
   * @return Object with any metadata that could be extracted (possibly none)
   */
  _getJSONLD: function(doc) {
    var scripts = this._getAllNodesWithTag(doc, ['script'])

    var jsonLdElement = this._findNode(scripts, function(el) {
      return el.getAttribute('type') === 'application/ld+json'
    })

    if (jsonLdElement) {
      try {
        // Strip CDATA markers if present
        var content = jsonLdElement.textContent.replace(
          /^\s*<!\[CDATA\[|\]\]>\s*$/g,
          ''
        )
        var parsed = JSON.parse(content)
        var metadata = {}
        if (
          !parsed['@context'] ||
          !parsed['@context'].match(/^https?\:\/\/schema\.org$/)
        ) {
          return metadata
        }

        if (!parsed['@type'] && Array.isArray(parsed['@graph'])) {
          parsed = parsed['@graph'].find(function(it) {
            return (it['@type'] || '').match(this.REGEXPS.jsonLdArticleTypes)
          })
        }

        if (
          !parsed ||
          !parsed['@type'] ||
          !parsed['@type'].match(this.REGEXPS.jsonLdArticleTypes)
        ) {
          return metadata
        }
        if (typeof parsed.name === 'string') {
          metadata.title = parsed.name.trim()
        } else if (typeof parsed.headline === 'string') {
          metadata.title = parsed.headline.trim()
        }
        if (parsed.author) {
          if (typeof parsed.author.name === 'string') {
            metadata.byline = parsed.author.name.trim()
          } else if (
            Array.isArray(parsed.author) &&
            parsed.author[0] &&
            typeof parsed.author[0].name === 'string'
          ) {
            metadata.byline = parsed.author
              .filter(function(author) {
                return author && typeof author.name === 'string'
              })
              .map(function(author) {
                return author.name.trim()
              })
              .join(', ')
          }
        }
        if (typeof parsed.description === 'string') {
          metadata.excerpt = parsed.description.trim()
        }
        if (parsed.publisher && typeof parsed.publisher.name === 'string') {
          metadata.siteName = parsed.publisher.name.trim()
        }
        return metadata
      } catch (err) {
        this.log(err.message)
      }
    }
    return {}
  },

  /**
   * Attempts to get excerpt and byline metadata for the article.
   *
   * @param {Object} jsonld — object containing any metadata that
   * could be extracted from JSON-LD object.
   *
   * @return Object with optional "excerpt" and "byline" properties
   */
  _getArticleMetadata: function(jsonld) {
    var metadata = {}
    var values = {}
    var metaElements = this._doc.getElementsByTagName('meta')

    // property is a space-separated list of values
    var propertyPattern = /\s*(dc|dcterm|og|twitter)\s*:\s*(author|creator|description|title|site_name)\s*/gi

    // name is a single value
    var namePattern = /^\s*(?:(dc|dcterm|og|twitter|weibo:(article|webpage))\s*[\.:]\s*)?(author|creator|description|title|site_name)\s*$/i

    // Find description tags.
    this._forEachNode(metaElements, function(element) {
      var elementName = element.getAttribute('name')
      var elementProperty = element.getAttribute('property')
      var content = element.getAttribute('content')
      if (!content) {
        return
      }
      var matches = null
      var name = null

      if (elementProperty) {
        matches = elementProperty.match(propertyPattern)
        if (matches) {
          // Convert to lowercase, and remove any whitespace
          // so we can match below.
          name = matches[0].toLowerCase().replace(/\s/g, '')
          // multiple authors
          values[name] = content.trim()
        }
      }
      if (!matches && elementName && namePattern.test(elementName)) {
        name = elementName
        if (content) {
          // Convert to lowercase, remove any whitespace, and convert dots
          // to colons so we can match below.
          name = name
            .toLowerCase()
            .replace(/\s/g, '')
            .replace(/\./g, ':')
          values[name] = content.trim()
        }
      }
    })

    // get title
    metadata.title =
      jsonld.title ||
      values['dc:title'] ||
      values['dcterm:title'] ||
      values['og:title'] ||
      values['weibo:article:title'] ||
      values['weibo:webpage:title'] ||
      values['title'] ||
      values['twitter:title']

    if (!metadata.title) {
      metadata.title = this._getArticleTitle()
    }

    // get author
    metadata.byline =
      jsonld.byline ||
      values['dc:creator'] ||
      values['dcterm:creator'] ||
      values['author']

    // get description
    metadata.excerpt =
      jsonld.excerpt ||
      values['dc:description'] ||
      values['dcterm:description'] ||
      values['og:description'] ||
      values['weibo:article:description'] ||
      values['weibo:webpage:description'] ||
      values['description'] ||
      values['twitter:description']

    // get site name
    metadata.siteName = jsonld.siteName || values['og:site_name']

    // in many sites the meta value is escaped with HTML entities,
    // so here we need to unescape it
    metadata.title = this._unescapeHtmlEntities(metadata.title)
    metadata.byline = this._unescapeHtmlEntities(metadata.byline)
    metadata.excerpt = this._unescapeHtmlEntities(metadata.excerpt)
    metadata.siteName = this._unescapeHtmlEntities(metadata.siteName)

    return metadata
  },

  /**
   * Check if node is image, or if node contains exactly only one image
   * whether as a direct child or as its descendants.
   *
   * @param Element
   **/
  _isSingleImage: function(node) {
    if (node.tagName === 'IMG') {
      return true
    }

    if (node.children.length !== 1 || node.textContent.trim() !== '') {
      return false
    }

    return this._isSingleImage(node.children[0])
  },

  /**
   * Find all <noscript> that are located after <img> nodes, and which contain only one
   * <img> element. Replace the first image with the image from inside the <noscript> tag,
   * and remove the <noscript> tag. This improves the quality of the images we use on
   * some sites (e.g. Medium).
   *
   * @param Element
   **/
  _unwrapNoscriptImages: function(doc) {
    // Find img without source or attributes that might contains image, and remove it.
    // This is done to prevent a placeholder img is replaced by img from noscript in next step.
    var imgs = Array.from(doc.getElementsByTagName('img'))
    this._forEachNode(imgs, function(img) {
      for (var i = 0; i < img.attributes.length; i++) {
        var attr = img.attributes[i]
        switch (attr.name) {
          case 'src':
          case 'srcset':
          case 'data-src':
          case 'data-srcset':
            return
        }

        if (/\.(jpg|jpeg|png|webp)/i.test(attr.value)) {
          return
        }
      }

      img.parentNode.removeChild(img)
    })

    // Next find noscript and try to extract its image
    var noscripts = Array.from(doc.getElementsByTagName('noscript'))
    this._forEachNode(noscripts, function(noscript) {
      // Parse content of noscript and make sure it only contains image
      var tmp = doc.createElement('div')
      tmp.innerHTML = noscript.innerHTML
      if (!this._isSingleImage(tmp)) {
        return
      }

      // If noscript has previous sibling and it only contains image,
      // replace it with noscript content. However we also keep old
      // attributes that might contains image.
      var prevElement = noscript.previousElementSibling
      if (prevElement && this._isSingleImage(prevElement)) {
        var prevImg = prevElement
        if (prevImg.tagName !== 'IMG') {
          prevImg = prevElement.getElementsByTagName('img')[0]
        }

        var newImg = tmp.getElementsByTagName('img')[0]
        for (var i = 0; i < prevImg.attributes.length; i++) {
          var attr = prevImg.attributes[i]
          if (attr.value === '') {
            continue
          }

          if (
            attr.name === 'src' ||
            attr.name === 'srcset' ||
            /\.(jpg|jpeg|png|webp)/i.test(attr.value)
          ) {
            if (newImg.getAttribute(attr.name) === attr.value) {
              continue
            }

            var attrName = attr.name
            if (newImg.hasAttribute(attrName)) {
              attrName = 'data-old-' + attrName
            }

            newImg.setAttribute(attrName, attr.value)
          }
        }

        noscript.parentNode.replaceChild(tmp.firstElementChild, prevElement)
      }
    })
  },

  /**
   * Removes script tags from the document.
   *
   * @param Element
   **/
  _removeScripts: function(doc) {
    this._removeNodes(this._getAllNodesWithTag(doc, ['script']), function(
      scriptNode
    ) {
      scriptNode.nodeValue = ''
      scriptNode.removeAttribute('src')
      return true
    })
    this._removeNodes(this._getAllNodesWithTag(doc, ['noscript']))
  },

  /**
   * Check if this node has only whitespace and a single element with given tag
   * Returns false if the DIV node contains non-empty text nodes
   * or if it contains no element with given tag or more than 1 element.
   *
   * @param Element
   * @param string tag of child element
   **/
  _hasSingleTagInsideElement: function(element, tag) {
    // There should be exactly 1 element child with given tag
    if (element.children.length != 1 || element.children[0].tagName !== tag) {
      return false
    }

    // And there should be no text nodes with real content
    return !this._someNode(element.childNodes, function(node) {
      return (
        node.nodeType === this.TEXT_NODE &&
        this.REGEXPS.hasContent.test(node.textContent)
      )
    })
  },

  _isElementWithoutContent: function(node) {
    return (
      node.nodeType === this.ELEMENT_NODE &&
      node.textContent.trim().length == 0 &&
      (node.children.length == 0 ||
        node.children.length ==
          node.getElementsByTagName('br').length +
            node.getElementsByTagName('hr').length)
    )
  },

  /**
   * Determine whether element has any children block level elements.
   *
   * @param Element
   */
  _hasChildBlockElement: function(element) {
    return this._someNode(element.childNodes, function(node) {
      return (
        this.DIV_TO_P_ELEMS.has(node.tagName) ||
        this._hasChildBlockElement(node)
      )
    })
  },

  /***
   * Determine if a node qualifies as phrasing content.
   * https://developer.mozilla.org/en-US/docs/Web/Guide/HTML/Content_categories#Phrasing_content
   **/
  _isPhrasingContent: function(node) {
    return (
      node.nodeType === this.TEXT_NODE ||
      this.PHRASING_ELEMS.indexOf(node.tagName) !== -1 ||
      ((node.tagName === 'A' ||
        node.tagName === 'DEL' ||
        node.tagName === 'INS') &&
        this._everyNode(node.childNodes, this._isPhrasingContent))
    )
  },

  _isWhitespace: function(node) {
    return (
      (node.nodeType === this.TEXT_NODE &&
        node.textContent.trim().length === 0) ||
      (node.nodeType === this.ELEMENT_NODE && node.tagName === 'BR')
    )
  },

  /**
   * Get the inner text of a node - cross browser compatibly.
   * This also strips out any excess whitespace to be found.
   *
   * @param Element
   * @param Boolean normalizeSpaces (default: true)
   * @return string
   **/
  _getInnerText: function(e, normalizeSpaces) {
    normalizeSpaces =
      typeof normalizeSpaces === 'undefined' ? true : normalizeSpaces
    var textContent = e.textContent.trim()

    if (normalizeSpaces) {
      return textContent.replace(this.REGEXPS.normalize, ' ')
    }
    return textContent
  },

  /**
   * Get the number of times a string s appears in the node e.
   *
   * @param Element
   * @param string - what to split on. Default is ","
   * @return number (integer)
   **/
  _getCharCount: function(e, s) {
    s = s || ','
    return this._getInnerText(e).split(s).length - 1
  },

  /**
   * Remove the style attribute on every e and under.
   * TODO: Test if getElementsByTagName(*) is faster.
   *
   * @param Element
   * @return void
   **/
  _cleanStyles: function(e) {
    if (!e || e.tagName.toLowerCase() === 'svg') return

    // Remove `style` and deprecated presentational attributes
    for (var i = 0; i < this.PRESENTATIONAL_ATTRIBUTES.length; i++) {
      e.removeAttribute(this.PRESENTATIONAL_ATTRIBUTES[i])
    }

    if (this.DEPRECATED_SIZE_ATTRIBUTE_ELEMS.indexOf(e.tagName) !== -1) {
      e.removeAttribute('width')
      e.removeAttribute('height')
    }

    var cur = e.firstElementChild
    while (cur !== null) {
      this._cleanStyles(cur)
      cur = cur.nextElementSibling
    }
  },

  /**
   * Get the density of links as a percentage of the content
   * This is the amount of text that is inside a link divided by the total text in the node.
   *
   * @param Element
   * @return number (float)
   **/
  _getLinkDensity: function(element) {
    var textLength = this._getInnerText(element).length
    if (textLength === 0) return 0

    var linkLength = 0

    // XXX implement _reduceNodeList?
    this._forEachNode(element.getElementsByTagName('a'), function(linkNode) {
      var href = linkNode.getAttribute('href')
      var coefficient = href && this.REGEXPS.hashUrl.test(href) ? 0.3 : 1
      linkLength += this._getInnerText(linkNode).length * coefficient
    })

    return linkLength / textLength
  },

  /**
   * Get an elements class/id weight. Uses regular expressions to tell if this
   * element looks good or bad.
   *
   * @param Element
   * @return number (Integer)
   **/
  _getClassWeight: function(e) {
    if (!this._flagIsActive(this.FLAG_WEIGHT_CLASSES)) return 0

    var weight = 0

    // Look for a special classname
    if (typeof e.className === 'string' && e.className !== '') {
      if (this.REGEXPS.negative.test(e.className)) weight -= 25

      if (this.REGEXPS.positive.test(e.className)) weight += 25
    }

    // Look for a special ID
    if (typeof e.id === 'string' && e.id !== '') {
      if (this.REGEXPS.negative.test(e.id)) weight -= 25

      if (this.REGEXPS.positive.test(e.id)) weight += 25
    }

    return weight
  },

  /**
   * Clean a node of all elements of type "tag".
   * (Unless it's a youtube/vimeo video. People love movies.)
   *
   * @param Element
   * @param string tag to clean
   * @return void
   **/
  _clean: function(e, tag) {
    var isEmbed = ['object', 'embed', 'iframe'].indexOf(tag) !== -1

    this._removeNodes(this._getAllNodesWithTag(e, [tag]), function(element) {
      // Allow youtube and vimeo videos through as people usually want to see those.
      if (isEmbed) {
        // First, check the elements attributes to see if any of them contain youtube or vimeo
        for (var i = 0; i < element.attributes.length; i++) {
          if (this.REGEXPS.videos.test(element.attributes[i].value)) {
            return false
          }
        }

        // For embed with <object> tag, check inner HTML as well.
        if (
          element.tagName === 'object' &&
          this.REGEXPS.videos.test(element.innerHTML)
        ) {
          return false
        }
      }

      return true
    })
  },

  /**
   * Check if a given node has one of its ancestor tag name matching the
   * provided one.
   * @param  HTMLElement node
   * @param  String      tagName
   * @param  Number      maxDepth
   * @param  Function    filterFn a filter to invoke to determine whether this node 'counts'
   * @return Boolean
   */
  _hasAncestorTag: function(node, tagName, maxDepth, filterFn) {
    maxDepth = maxDepth || 3
    tagName = tagName.toUpperCase()
    var depth = 0
    while (node.parentNode) {
      if (maxDepth > 0 && depth > maxDepth) return false
      if (
        node.parentNode.tagName === tagName &&
        (!filterFn || filterFn(node.parentNode))
      )
        return true
      node = node.parentNode
      depth++
    }
    return false
  },

  /**
   * Return an object indicating how many rows and columns this table has.
   */
  _getRowAndColumnCount: function(table) {
    var rows = 0
    var columns = 0
    var trs = table.getElementsByTagName('tr')
    for (var i = 0; i < trs.length; i++) {
      var rowspan = trs[i].getAttribute('rowspan') || 0
      if (rowspan) {
        rowspan = parseInt(rowspan, 10)
      }
      rows += rowspan || 1

      // Now look for column-related info
      var columnsInThisRow = 0
      var cells = trs[i].getElementsByTagName('td')
      for (var j = 0; j < cells.length; j++) {
        var colspan = cells[j].getAttribute('colspan') || 0
        if (colspan) {
          colspan = parseInt(colspan, 10)
        }
        columnsInThisRow += colspan || 1
      }
      columns = Math.max(columns, columnsInThisRow)
    }
    return { rows: rows, columns: columns }
  },

  /**
   * Look for 'data' (as opposed to 'layout') tables, for which we use
   * similar checks as
   * https://searchfox.org/mozilla-central/rev/f82d5c549f046cb64ce5602bfd894b7ae807c8f8/accessible/generic/TableAccessible.cpp#19
   */
  _markDataTables: function(root) {
    var tables = root.getElementsByTagName('table')
    for (var i = 0; i < tables.length; i++) {
      var table = tables[i]
      var role = table.getAttribute('role')
      if (role == 'presentation') {
        table._readabilityDataTable = false
        continue
      }
      var datatable = table.getAttribute('datatable')
      if (datatable == '0') {
        table._readabilityDataTable = false
        continue
      }
      var summary = table.getAttribute('summary')
      if (summary) {
        table._readabilityDataTable = true
        continue
      }

      var caption = table.getElementsByTagName('caption')[0]
      if (caption && caption.childNodes.length > 0) {
        table._readabilityDataTable = true
        continue
      }

      // If the table has a descendant with any of these tags, consider a data table:
      var dataTableDescendants = ['col', 'colgroup', 'tfoot', 'thead', 'th']
      var descendantExists = function(tag) {
        return !!table.getElementsByTagName(tag)[0]
      }
      if (dataTableDescendants.some(descendantExists)) {
        this.log('Data table because found data-y descendant')
        table._readabilityDataTable = true
        continue
      }

      // Nested tables indicate a layout table:
      if (table.getElementsByTagName('table')[0]) {
        table._readabilityDataTable = false
        continue
      }

      var sizeInfo = this._getRowAndColumnCount(table)
      if (sizeInfo.rows >= 10 || sizeInfo.columns > 4) {
        table._readabilityDataTable = true
        continue
      }
      // Now just go by size entirely:
      table._readabilityDataTable = sizeInfo.rows * sizeInfo.columns > 10
    }
  },

  /* convert images and figures that have properties like data-src into images that can be loaded without JS */
  _fixLazyImages: function(root) {
    this._forEachNode(
      this._getAllNodesWithTag(root, ['img', 'picture', 'figure']),
      function(elem) {
        // In some sites (e.g. Kotaku), they put 1px square image as base64 data uri in the src attribute.
        // So, here we check if the data uri is too short, just might as well remove it.
        if (elem.src && this.REGEXPS.b64DataUrl.test(elem.src)) {
          // Make sure it's not SVG, because SVG can have a meaningful image in under 133 bytes.
          var parts = this.REGEXPS.b64DataUrl.exec(elem.src)
          if (parts[1] === 'image/svg+xml') {
            return
          }

          // Make sure this element has other attributes which contains image.
          // If it doesn't, then this src is important and shouldn't be removed.
          var srcCouldBeRemoved = false
          for (var i = 0; i < elem.attributes.length; i++) {
            var attr = elem.attributes[i]
            if (attr.name === 'src') {
              continue
            }

            if (/\.(jpg|jpeg|png|webp)/i.test(attr.value)) {
              srcCouldBeRemoved = true
              break
            }
          }

          // Here we assume if image is less than 100 bytes (or 133B after encoded to base64)
          // it will be too small, therefore it might be placeholder image.
          if (srcCouldBeRemoved) {
            var b64starts = elem.src.search(/base64\s*/i) + 7
            var b64length = elem.src.length - b64starts
            if (b64length < 133) {
              elem.removeAttribute('src')
            }
          }
        }

        // also check for "null" to work around https://github.com/jsdom/jsdom/issues/2580
        if (
          (elem.src || (elem.srcset && elem.srcset != 'null')) &&
          elem.className.toLowerCase().indexOf('lazy') === -1
        ) {
          return
        }

        for (var j = 0; j < elem.attributes.length; j++) {
          attr = elem.attributes[j]
          if (attr.name === 'src' || attr.name === 'srcset') {
            continue
          }
          var copyTo = null
          if (/\.(jpg|jpeg|png|webp)\s+\d/.test(attr.value)) {
            copyTo = 'srcset'
          } else if (/^\s*\S+\.(jpg|jpeg|png|webp)\S*\s*$/.test(attr.value)) {
            copyTo = 'src'
          }
          if (copyTo) {
            //if this is an img or picture, set the attribute directly
            if (elem.tagName === 'IMG' || elem.tagName === 'PICTURE') {
              elem.setAttribute(copyTo, attr.value)
            } else if (
              elem.tagName === 'FIGURE' &&
              !this._getAllNodesWithTag(elem, ['img', 'picture']).length
            ) {
              //if the item is a <figure> that does not contain an image or picture, create one and place it inside the figure
              //see the nytimes-3 testcase for an example
              var img = this._doc.createElement('img')
              img.setAttribute(copyTo, attr.value)
              elem.appendChild(img)
            }
          }
        }
      }
    )
  },

  _getTextDensity: function(e, tags) {
    var textLength = this._getInnerText(e, true).length
    if (textLength === 0) {
      return 0
    }
    var childrenLength = 0
    var children = this._getAllNodesWithTag(e, tags)
    this._forEachNode(
      children,
      child => (childrenLength += this._getInnerText(child, true).length)
    )
    return childrenLength / textLength
  },

  /**
   * Clean an element of all tags of type "tag" if they look fishy.
   * "Fishy" is an algorithm based on content length, classnames, link density, number of images & embeds, etc.
   *
   * @return void
   **/
  _cleanConditionally: function(e, tag) {
    if (!this._flagIsActive(this.FLAG_CLEAN_CONDITIONALLY)) return

    // Gather counts for other typical elements embedded within.
    // Traverse backwards so we can remove nodes at the same time
    // without effecting the traversal.
    //
    // TODO: Consider taking into account original contentScore here.
    this._removeNodes(this._getAllNodesWithTag(e, [tag]), function(node) {
      // First check if this node IS data table, in which case don't remove it.
      var isDataTable = function(t) {
        return t._readabilityDataTable
      }

      var isList = tag === 'ul' || tag === 'ol'
      if (!isList) {
        var listLength = 0
        var listNodes = this._getAllNodesWithTag(node, ['ul', 'ol'])
        this._forEachNode(
          listNodes,
          list => (listLength += this._getInnerText(list).length)
        )
        isList = listLength / this._getInnerText(node).length > 0.9
      }

      if (tag === 'table' && isDataTable(node)) {
        return false
      }

      // Next check if we're inside a data table, in which case don't remove it as well.
      if (this._hasAncestorTag(node, 'table', -1, isDataTable)) {
        return false
      }

      if (this._hasAncestorTag(node, 'code')) {
        return false
      }

      var weight = this._getClassWeight(node)

      this.log('Cleaning Conditionally', node)

      var contentScore = 0

      if (weight + contentScore < 0) {
        return true
      }

      if (this._getCharCount(node, ',') < 10) {
        // If there are not very many commas, and the number of
        // non-paragraph elements is more than paragraphs or other
        // ominous signs, remove the element.
        var p = node.getElementsByTagName('p').length
        var img = node.getElementsByTagName('img').length
        var li = node.getElementsByTagName('li').length - 100
        var input = node.getElementsByTagName('input').length
        var headingDensity = this._getTextDensity(node, [
          'h1',
          'h2',
          'h3',
          'h4',
          'h5',
          'h6',
        ])

        var embedCount = 0
        var embeds = this._getAllNodesWithTag(node, [
          'object',
          'embed',
          'iframe',
        ])

        for (var i = 0; i < embeds.length; i++) {
          // If this embed has attribute that matches video regex, don't delete it.
          for (var j = 0; j < embeds[i].attributes.length; j++) {
            if (this.REGEXPS.videos.test(embeds[i].attributes[j].value)) {
              return false
            }
          }

          // For embed with <object> tag, check inner HTML as well.
          if (
            embeds[i].tagName === 'object' &&
            this.REGEXPS.videos.test(embeds[i].innerHTML)
          ) {
            return false
          }

          embedCount++
        }

        var linkDensity = this._getLinkDensity(node)
        var contentLength = this._getInnerText(node).length

        var haveToRemove =
          (img > 1 && p / img < 0.5 && !this._hasAncestorTag(node, 'figure')) ||
          (!isList && li > p) ||
          input > Math.floor(p / 3) ||
          (!isList &&
            headingDensity < 0.9 &&
            contentLength < 25 &&
            (img === 0 || img > 2) &&
            !this._hasAncestorTag(node, 'figure')) ||
          (!isList && weight < 25 && linkDensity > 0.2) ||
          (weight >= 25 && linkDensity > 0.5) ||
          (embedCount === 1 && contentLength < 75) || embedCount > 1
        return haveToRemove
      }
      return false
    })
  },

  /**
   * Clean out elements that match the specified conditions
   *
   * @param Element
   * @param Function determines whether a node should be removed
   * @return void
   **/
  _cleanMatchedNodes: function(e, filter) {
    var endOfSearchMarkerNode = this._getNextNode(e, true)
    var next = this._getNextNode(e)
    while (next && next != endOfSearchMarkerNode) {
      if (filter.call(this, next, next.className + ' ' + next.id)) {
        next = this._removeAndGetNext(next)
      } else {
        next = this._getNextNode(next)
      }
    }
  },

  /**
   * Clean out spurious headers from an Element.
   *
   * @param Element
   * @return void
   **/
  _cleanHeaders: function(e) {
    let headingNodes = this._getAllNodesWithTag(e, ['h1', 'h2'])
    this._removeNodes(headingNodes, function(node) {
      let shouldRemove = this._getClassWeight(node) < 0
      if (shouldRemove) {
        this.log('Removing header with low class weight:', node)
      }
      return shouldRemove
    })
  },

  /**
   * Check if this node is an H1 or H2 element whose content is mostly
   * the same as the article title.
   *
   * @param Element  the node to check.
   * @return boolean indicating whether this is a title-like header.
   */
  _headerDuplicatesTitle: function(node) {
    if (node.tagName != 'H1' && node.tagName != 'H2') {
      return false
    }
    var heading = this._getInnerText(node, false)
    this.log('Evaluating similarity of header:', heading, this._articleTitle)
    return this._textSimilarity(this._articleTitle, heading) > 0.75
  },

  _flagIsActive: function(flag) {
    return (this._flags & flag) > 0
  },

  _removeFlag: function(flag) {
    this._flags = this._flags & ~flag
  },

  _isProbablyVisible: function(node) {
    // Have to null-check node.style and node.className.indexOf to deal with SVG and MathML nodes.
    return (
      (!node.style || node.style.display != 'none') &&
      !node.hasAttribute('hidden') &&
      //check for "fallback-image" so that wikimedia math images are displayed
      (!node.hasAttribute('aria-hidden') ||
        node.getAttribute('aria-hidden') != 'true' ||
        (node.className &&
          node.className.indexOf &&
          node.className.indexOf('fallback-image') !== -1))
    )
  },

  /**
   * Runs readability.
   *
   * Workflow:
   *  1. Prep the document by removing script tags, css, etc.
   *  2. Build readability's DOM tree.
   *  3. Grab the article content from the current dom tree.
   *  4. Replace the current DOM tree with the new one.
   *  5. Read peacefully.
   *
   * @return void
   **/
  parse: function() {
    // Avoid parsing too large documents, as per configuration option
    if (this._maxElemsToParse > 0) {
      var numTags = this._doc.getElementsByTagName('*').length
      if (numTags > this._maxElemsToParse) {
        throw new Error(
          'Aborting parsing document; ' + numTags + ' elements found'
        )
      }
    }

    // Unwrap image from noscript
    this._unwrapNoscriptImages(this._doc)

    // Extract JSON-LD metadata before removing scripts
    var jsonLd = this._disableJSONLD ? {} : this._getJSONLD(this._doc)

    // Remove script tags from the document.
    this._removeScripts(this._doc)

    this._prepDocument()

    var metadata = this._getArticleMetadata(jsonLd)
    this._articleTitle = metadata.title

    var articleContent = this._grabArticle()
    if (!articleContent) return null

    this.log('Grabbed: ' + articleContent.innerHTML)

    this._postProcessContent(articleContent)

    // If we haven't found an excerpt in the article's metadata, use the article's
    // first paragraph as the excerpt. This is used for displaying a preview of
    // the article's content.
    if (!metadata.excerpt) {
      var paragraphs = articleContent.getElementsByTagName('p')
      if (paragraphs.length > 0) {
        metadata.excerpt = paragraphs[0].textContent.trim()
      }
    }

    var textContent = articleContent.textContent
    return {
      title: this._articleTitle,
      byline: metadata.byline || this._articleByline,
      dir: this._articleDir,
      content: this._serializer(articleContent),
      textContent: textContent,
      length: textContent.length,
      excerpt: metadata.excerpt,
      siteName: metadata.siteName || this._articleSiteName,
    }
  },
}

if (typeof module === 'object') {
  module.exports = Readability
}
